Google traffic persists despite disable-background-networking and related flags

[Harvester15]

CEF/CefSharp version: 146.x and 149.x (reproduced on both)

We're trying to run CefSharp in a restricted enterprise environment where no outbound Google traffic is permitted.

Even when loading only about:blank and using a fresh cache/profile, Chromium still generates outbound requests to Google-owned endpoints.

Configuration:

settings.CefCommandLineArgs.Add("disable-sync", "1");
settings.CefCommandLineArgs.Add("disable-component-update", "1");
settings.CefCommandLineArgs.Add("disable-gaia-services", "1");
settings.CefCommandLineArgs.Add("disable-background-networking", "1");
settings.CefCommandLineArgs.Add("disable-extensions");
settings.CefCommandLineArgs.Add("metrics-recording-only", "1");
settings.CefCommandLineArgs.Add("no-first-run", "1");
settings.CefCommandLineArgs.Add("disable-default-apps", "1");
settings.CefCommandLineArgs.Add("disable-domain-reliability", "1");
settings.CefCommandLineArgs.Add("disable-features", "AutofillServerCommunication,MediaRouter,Translate,NetworkTimeServiceQuerying,NetworkQualityEstimator,OptimizationGuideOnDeviceModel");

NetLog still shows requests such as:

• http://clients2.google.com/time/1/current
  Source Type: NETWORK_QUALITY_ESTIMATOR

and also preconnect activity to:

• https://www.google.com/
• https://accounts.google.com/

From the NetLog it appears these requests originate from Chromium itself rather than page content.

Question:
Is there currently a supported way in CEF/CefSharp to completely disable all Google/Chromium background requests (including Network Quality Estimator, time service, preconnects, account checks, etc.), or is a custom CEF build / network-level blocking required?

netlog.json